I have a form as
When accessing in C# code-behind via
That's just not the way ASP.NET works. You can selectively set certain controls to post to a different page, however. This is called Cross Page Posting. See: http://msdn.microsoft.com/en-us/library/ms178139(v=vs.100).aspx. To perform a cross page postback with a button for example see: http://msdn.microsoft.com/en-us/library/system.web.ui.webcontrols.button.postbackurl.aspx. Basically, you simply set the PostBackUrl for the button.